Conventionally, induction heating cookers of this type have been adapted to perform boiling detection operations after start of heating, to determine the viscosities and the volumes of objects to be cooked within cooking containers (such as pans) based on the temperature and input electric power at the time boiling is detected, and temperature changing patterns until the occurrence of the boiling, and to determine electric power necessary to perform heating after the boiling. Conventional induction heating cookers have been adapted to have a stewing mode for performing scorching detection in order to determine the occurrence of scorching of an object to be cooked to the pan bottom, if the temperature of the bottom surface of the cooking container (the pan bottom) is abruptly raised to above a predetermined value, since a soup stock has been run out within the cooking container being heated (refer to Unexamined Japanese Patent Publication No. H10-149875 (hereinafter, abbreviated as Patent Literature 1), for example). Further, for conventional induction heating cookers, there have been suggested structures for determining the occurrence of scorching, if a detected temperature of a cooking container being heated abruptly rises (refer to Unexamined Japanese Patent Publication No. 2007-115515 (hereinafter, abbreviated as Patent Literature 2), for example).
FIG. 9 is a block diagram of a conventional induction heating cooker, and FIG. 10 is a flow chart illustrating operations of the conventional induction heating cooker illustrated in FIG. 9.
Referring to FIG. 9, a top plate 101 is a plate made of a crystallized ceramic, which is provided in an upper surface of the induction heating cooker, and a heating coil 103 is provided under the top plate 101. When a pan 102 as a cooking container is heated, the pan 102 is placed on the top plate 101, such that a bottom of the pan faces the heating coil 103. An inverter circuit 108a, which includes a switching device and a resonant capacitor, constitutes an inverter in cooperation with the heating coil 103 and supplies a high-frequency electric current to the heating coil 103. A control portion 107 performs ON and OFF control on the switching device in the inverter circuit 108a for controlling the heating output. In order to detect the temperature of the bottom surface of the pan 102 as a cooking container, a thermistor 104 as a thermo-sensitive device is provided on the back surface of the top plate 101 on which the pan 102 is placed such that the thermistor 104 is in contact with the back surface to determine the temperature of the back surface of the top plate 101. The thermistor 104 outputs, to the control portion 107, detection signals corresponding to the temperature of the back surface of the top plate 101. A manipulation portion 101 manipulated by a user is provided with an output setting portion 110a, a heating-start key 110b for starting heating operations, and a control-mode selection key 110c for selecting operation modes. The output setting portion 110a is provided with a down key 110aa that decreases the set output value by a single step every time the down key 110aa is pressed, during operations in a heating mode, and an up key 110ab which increases the set output value by a single step every time the up key 110ab is pressed.
Next, operations of the conventional induction heating cooker having the structure as described above will be described, with reference to FIG. 10. If a power-supply switch 106 is turned on (S301), the control portion 107 is brought into a standby mode. In the standby mode, the control portion 107 stops heating operations, in a state where it is possible to select a single operation mode, out of a plurality of operation modes including a heating mode and a stewing mode, by manipulating the control-mode selection key 110c in the manipulation portion 110. In the standby mode, when an operation mode is selected (S302), and the heating-start key 110b is pressed (S303), a heating operation is started in the selected operation mode. For example, when the stewing mode is selected and a heating operation is started (Yes in S304), the control portion 107 prohibits changing the set output value through the output setting portion 110a, and performs a boiling detection operation and then automatically controls the heating output, as described in Patent Literature 1. If an abnormal temperature rise in the pan 102 is detected from detection signals from the thermistor 104, a scorching detection function for detecting scorching is exerted (S306). If, for example, the heating mode, rather than the stewing mode, is selected, and a heating operation is started (No in S304), the control portion 107 prohibits the scorching detection function from being exerted (S305). At this time, changing of the set output value through the output setting portion 110a is allowed.    PLT 1: Unexamined Japanese Patent Publication No. H10-149875    PLT 2: Unexamined Japanese Patent Publication No. 2007-115515